Internal-combustion engine power plant



5 Sheets-Sheetl l L. F. R. FELL @m ,v/Evi a v,

o m NOVR EQU` INTERNAL-COMBUSTION ENGINE POWER PLANT m wf II l March 18, 1952 Filed Dec. 26, 1947 Attornelf IMarch I8, 1952 L. F. R. FELL IINTERNAL.-COMBUSTION ENGINE POWER PLANT Filed Dec. 26, 1947 5 Sheeiis-Sheet 2 F/GZ i AS- /d//hy 4 spr/n35 engagmg lh Sequence m eco 800 'ooo :zoo 14o@ Iaco RAM.

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nvenlor Fell Atlorneys March 18, 1952 F. R. FELL 2,589,788

INTERNAL-COMBUSTION ENGINE POWER PLANT Filed DSC. 26, 1947 5 ShetS-Shee 5 A llomeys IMarch 18, 1952 F. R. FELL INTEENAL-COMEUSTION ENGINE POWER PLANT 5 Sheets-Sheet 4 Filed Dec. 26, 1947 Inventor 0V/S y wlw A Homey:

March 18, 1952 l.. F. R. Fl-:LL 2,589,788

INTEENAL-COMBUSTION ENGINE POWER PLANT Filed Dec. 2e, 1947 5 sheets-sheet Patented Mar. 18, 1952 INTERNAL-COMBUSTION ENGINE POWER PLAN Louis Frederick Rudston Fell, Littleover, England, assignor to Fell Developments Limited, London, England, a British company Application December 26, 1947, Serial N o. 793,903 In Great Britain October 13, 1947 15 claims. (c1. (so-97) This present invention relates to an internal combustion engine power plant embodying two or more vengines of the compression ignition type, these engines being supercharged at a pressure which. decreases as their rotational speed"v inor compressors.

In a multiple engine power plant it is desirable rthat the total load on the plant shall be shared as equally as possible between the several engines in operation at any one time irrespective of the running speed. In the interests of flexibility of the plantit is desirable that it shall be possible to run' on load any one or any combination of the engines comprised in the plant. Forcertain uses'such as for example self-propelled vehicles,'it is of importance that the engines be caused to'contribute successively their individual torques to the total torque smoothly and/many desired order and with no discontinuity in the final'output torque of the plant, whileputting individual engines on load or while taking them off load, and also to be able to disconnect completely any or all of the engines. f

The objectf of the present invention is to provide a power plant which shall fulfil these requirements the improved plant comprising one or more units in each of which are two engines.

According to this invention a power unit comprises in combination two main internal combustion engines operating with compression ignition, means including one or more compressors driven independently of the main engines for supercharging those engines at a pressure which decreases as the rotational speed of each main engine increases, separate governors respectively controlling the fuel injection pump of each main engine, means for varying the speed setting of each governor, a differential gear, means whereby each main engine drives a sun wheel of this gear through a variable filling iiuidcoupling, means for transmitting power from the planet-carrying member of the said gear to the mechanism to be driven by the power unit, and a unidirectional brake device operative on veach sun wheel of the said gear, the whole unit con.-

Astruction when in operation enabling the torquesc of. onevnorboth of the main engines to be trans-4 mittediinusuccession or in combination to the mechanism which is driven thereby and in a Vway which avoids sharp fluctuations or discontinuity in the final output torque. The variable v fluid coupling used is conveniently of the scoopcreases, by an independently driven compressor y pression ignition'and this engine has a governor with means for varying the speed setting thereof,

the governor controlling the delivery of the fuel;

injection pump to the engine;

Each governor where it is for a'main engine or for an auxiliary engine driving a compressor, is of the centrifugal type and the variation in its speed setting is effected by movement of the abutment of one or more springs which control the operation of the governor. In the case of the governor of each auxiliary engine the movement of the spring abutment is actuated .or controlled by means responsive to the boost pressure of the main engines. Servomotors actuated by liquid pressure are employed-on the one hand to transmit to the spring abutment the movement which effects the speed setting of the governor, and on the other hand to transmit from each governor the movement which effects the speed regulation of the engine with which the governor is associated.

Each unidirectional brake device is conveniently of the self-wrapping type which will grip automatically and hold stationary a brake drum when this tends to rotate in one direction but will automatically release the brake drum when it is rotated in the opposite direction.

In the transmission of power from two of the foregoing units the planet-carrying member of the differential gear `of each power unit may be rotationally connected to the sun wheel of a separate differential gear whose planet-carrying member is rotationally connected to the mechanism which is to be driven by the power plant. p

1 There is combined with each mainengine an automatic 'control system comprising means whereby the amount of fuel delivered by the fuel injection pump of the main engine is varied in accordance with the speed of the engine and also in accordance with the -boost pressure of the engine.

Each engine is controlled by hydraulic means and the liquid under pressure employed in the hydraulic control is conveniently obtained from the lubricating oil pressure system of the engine, means being provided whereby if the pressure in this system falls below a predetermined gure the automatic control for setting the fuel injection pump delivery will be overridden automatically and the delivery of the fuel by the pump will be cut off.

The improved power plant in one form in which it may be carried out in practice is illustrated in the accompanying drawings. In these drawings:

Figure 1 shows diagrammatically a power plantl Figure 4 is a diagrammaticlayout ofthe-foon;

trols for each auxiliary engine which drives air compressor.

Figure 5 is a longitudinal sectional'elevationl of a variable speed centrifugal governor combined with a servomotor and suitable yfor use with-- each of the engines.

FigureI 6 is. a, section. ont the line. in, Figure 5.

Figure 7 is a diagram showingl the approxirnaterx speed ranges coveredby the combinationofi the four governor springswhich. come1 into operationin sequence..

. Incarrying (the. present.. invention.. into effect asshown in` Figure .1.. and by.` way of examplein aftwounitform suitable.. for a. self propelledV vehicle.. such as al railway locomotive, therel arefQul; internal combustionengines A, .B.C and'Doperating with.v compression ignition-1 These.y engines. may conveniently beY of. ther V type and.. each, may comprise twelve cylinders.

Engines A.l and B. constitute. one, power while enginesCand D formthe second unit.`

The engines A and Bare supplied with air'by.. afcompressor 2. driven by.` an auxiliary engines?! whh is. preferably. of. the; compression.v ignition type. The, compressor. 2.de1iv.ersair thlougl'i4 va pipe 4 to the manifolds 5 of theenines.A andBL A, spring loaded relief valve E. isprovided on .the pipe14and thisvalve may have means to .enable itto bemanuallyopenedlwhen required.

Similarly. engines C. and. D. are. supercharged bref compressor. 1, driven by an auxiliaryy engine 8 and` delivering air by a, pipe 9 tothe manifolds in. A Spring.loadedireliefvalve ||,.Smil'ar. to. the valve, is provided onutheupipe 9,., A balancing pipe I 2. is .provided toconnect the pipesa'nd. and; this Ypipe l2v may be` provdedwth. valve. Ilmo. enable thepinesa and 9 ,tobeisolatedgfromi oneanother.

The erenksnafts. ofthe. engines A and; B are. Coupled. to the. innntelefrrientsof variable. filling lluid., couplings. 13. andil. Toreonel oscillation damning.` devices. I5.1 and.. L6` may. be... RIOVIS. 11113.53: tweenthe engines` andthe. uidleouplinen. Slmfl ilarly fluidV couplings l 'ljV and I 8; andgdamping devices |9 vand, 2i) are provided' for enginesC andD.

The variable filling fluid couplings are offthe scoopfcpntrolled type, actuation of the scoops being., controlled by levers.. 2L. 22; 23vk and; 24 through suitable linkages..

Shafts are. in. eeen. cese. directly. eoupledi at one l.en d to the.l outputY element ofv` their respective fluid.. couplings and attheir. other. ends. to. Sun wheels ,2.6.; 2.1. 2.8.1and 2910i -two differential gears; The nlanet. carrying, members' 39,'` 3|.' of' these gears are connected'A through appropriate gearing 35a, 30o to the sun wheels 32 and 33. o fa third.. differential gear. The planet Carrying member Softhe. thirddlferentalis Connected by. Suitable gearingv 34a.. 34D. with. adrivine. axle 35 of the vehicle. A gear" train connects the planet. carrying member. 3.4. andthe axle 352ml mayconveniently include areversing -gear which 4 is shown diagrammatically as a pinion 36 permanently meshed with two crown wheels 31 and 38 mounted freely on a shaft 39 and adapted to be alternativelyy connectedto the shaft 39 by dog clutches 4.8 and 4 l.

v It will be 'understood that when a' two unit four engine plant is applied to a purpose other than propelling a vehicle final drive shaft 42 is conneet/.ed to theappropriate part of the machine to which power is to be supplied.

Invorder to enable the torque of one of the engines of; a` plant to be transmitted to the nal drivev shaft LlZNwhen the fluid couplings of the other engines of the plant are empty and conse- Aquentlvare incapable of oiferingresistance to rotation of their respective sun wheels, means are provided to hold these sun wheels. against backward rotation. These means may take the form of. unidirectional brakes 43, 44, 45 and.. 46 such asfor example self-wrapping brakesk which will automatically grip and' hold stationary their associatedl brake drums when these drums tend;

to rotate in a backward direction but which autorrlaticallyy allow the drums to rotate freely in'aY forward direction.

Figure 2 is al diagrammatic illustration of. a unidirectional braking device in which |'3.3.is^ a brakedrunr mounted on a` shaft 25. Brake shoes |34* arelpivoted on links |35 and' |38; The'links.. |35 and; |38 a-re suspended from a rocking4 beam |36 pivoted on a support |31.A The'link1l35car.- ries a. bellcrankl lever |39 pivoted to its lower end'. Qne end ofthe lever |39'is connected'by a. link |40 ,to an anchoragev |4'|. The otherarm of the bell crank lever |39` isconnected; by a rod- |42 pin jointed` on the link |38 at one end and provided' with a screw thread at'itsother-endzjl An, adjustinghand wheel |43 is screwedon to thgrcnil I42 andA b ears againstfthe short arm'of" theA bel-l, crank. A spring |44'tends to tipj the;A

lever' |36" inra clockwise direction. If the'drurnV I33'moves in a clockwise direction the shoe |3j4" carried by the link' |35A tends to lift theleft hand endofthe beam |35' at'the same timethat the spring, I44^is tendingtodepress the right hand end .ofthe beam |36.; Anymovement of-'thelink |35 upwardf tends totip theybellv crankin an anticlockwise direction putting a pull on rod- |42 and thus'causing the shoes |34 to grip the drum |33. Obviously, any rotationof' the drum- |-33fin1 anLanti-clockwise direction willv release the shoes from the-drum. l

Inapowerplant embodying a number offen;

' gines it is desirable to provide safeguards torero--l tectthev engines Vagainst damage certain'- circumstances. ForV example; should thev lubricate y ingoilA pressure Vfall-below a predetermined value elo it is' desirable thatgthat particular engine should automatically be shut down. Similarly-should thesuperchargeair pressure to a^ particular engine' fall belowl av value corresponding-to---the quantity offuel being supplied tothat engine-it isV desirable# that the amount of-'fuel should be appropriately reduced;

ForY the purpose'of controlling the torque de veloped by4 the individual engines andmaintaining the speed' ofthe enginesat the -desired=value, the engines areA each `providedfw-ith' a centrifugal type Variablespeedgovernor. In the preferred form of governor the variation-in speed; setting-g is obtainedl by moving`A the abutmentof'fthe gnv'- ernor spring or springs. In order -to cover a Wide range Ofspeedand to obtain thedesired governor characteristic'itl may; be desirable to employ a number ofsprings, say four, which engage-'the of a ii'oating lever 68 by a pin joint 66.

governor plunger in sequence so that as each additional spring engages it adds its load to that of the spring or sp-rings already engaged.

Figure 3 is a diagrammatic layout of controls to be mounted on each main engine. The layout of controls is also shown in a simplified manner in Figure l for the engine-A, i't-being understood that similar mechanisms are provided forv the engines B, C and D. For the purpose of avoiding unnecessary complexity of the drawing, however, these mechanisms are omitted from the engines B, C and D in Figure 1. It will be understood that each engine is rprovided with its owen fuel injection pump 41-and that for any given set of conditions the torque produced bythe engine will be determined by the amount 'of fuel which the pump is permitted to supplyvto the engine. A rod 48 when moved towardsY the right will cause the injected fuel quantity to increase and vice versa. A spring 4S tends to move the rod 48 to the left, i.e. towards stop or no fuel position. The end of the rod 48 is engaged by the end of one arm of a lever 58 the end 5| of the other arm of which is pivoted to the end of a rod 52 of a piston 53 vmovablein opposition to a spring 54. 'I'he piston 53 slides in a cylinder 55 wherein it is subjected through ar pipe to thelubricating voilpressure of the engine. So long as the engine is running and the oil pressurefis maintained above a predetermined value the piston 53 will be pressed hard against the end of the cylinder 55 as shown. In this condition the point 5| may be considered as a Xed pivotlng point 'for the whole lever 56. hand should the oil pressure fall below a certain predetermined value the piston 53 will move tothe right and the rod 48 willl move to the stop position thus shutting the engine down, the lever 50 then turning about the pivot 66 in its length.

In all `normal circumstances the movement of the rod 48 is effected by the movement of servomotor piston 56 in a cylinder 51. A rod. 58 extending from the piston 56 is connected to the lever 50 by a link 59 which extends from the pivot 66 on the lever 56 to the pivot 6| atv the end of the piston rod 58. The piston 56 is urged to the left by a spring 62 tending to shut down the engine. The admission and release of liquid to and from the cylinder 51 are controlled by a piston valve 63 which'cooperates with a port 64 in the wall of the cylinder 51. `Sufficient movement of the valve 63 to the right as shown in Figure 3 releases liquid from the cylinder and suflicient movement of the valve to the left admits liquid to the cylinder. In an intermediate positionthe valve 63 obstructs the port 64 and thus locks up the liquid inthe cylinder 51. A port 65 in the wall of the cylinder in which moves the valve 63 is connected to a supply of liquidunder pressureand a port 66 at the end of this cylinder is connected with a liquid storage vessel.

In some cases the liquid may be the lubricating oi1 of the engine. The valve 63 has a rod 61 to the end of which is pivoted one end The opposlteend of the lever 68 is pivoted at 10 .toa rod 1| of'a piston 12 of a servomotor the piston being movable in a cylinder 13. The "piston12 is loaded on one side 'by a spring 14 and" on the vother side by an opposing lighter rated spring 1.5. A port 16 at the endof the "cylinder 13 is connected by a suitable pipe 13a OnA the other I with the air supply pipe 4 of the engine. In# crease in boost pressure will tend to move the piston 12 to right andivice versa. v

A point 11 in theifloating lever 68 intermediate between the '.'ends 69 and 10 is connected by pivots and a link 118 with a point 19 in the length of a floating lever 80. At one end the lever is pivoted lat 6| to the piston rod 58 and the opposite endl is pivoted at 85 to a link 8| which in turn"is`connected to the end of a lever 82 on a rock ,shaft 83. The angular position of the rock shaft 83 and consequently of the lever 82 isdependent on the attitude or relative positionofgovernor weights 84 at anyinstant. A rise infengine speed tends to move the weights 84 outwards and swing the lever 82 clockwise thus moving thepin joint 85 to the "right as'shown vin Figure 3. Leaving "the detailed description'of the governor until later the functioning of the devices just described is as follows. Assumingthe engine to be running under steady conditions then the piston 53 will be held to the left 'against its stop and the. pivot at the point 5I maybe regarded as fixed in space. Should the load on the engine increase then the engine speed will tend to fall and the weights 84 'to come inwards thus moving the arm 82 counterclockwise. Through the link 8| the point 85 will be Amoved tothe left'. andv so also` will be moved the points 19 and -69 and consequently 'the valve 63. Thereupon liquid under pressure willl be admitted to the cylinder 51 moving the piston 56 to the right thus swinging the lever 58' about the pivot at the point 5I and moving therod 48 to .the rightto give more fuel to the engine to increase its torque and thus balance tliedincrease in load and restore the. speed to its intended value. It will be realised that as the piston 56 moved to the right in the above operation the point 19 also moved to the right Jth'us tendingv to cancel the previous movement 'at 16 to the left and to bring the valve 63 to a mean settled position with the port 64 closed.`

Again, assuming a steady'running condition.

if 'the supercharge pressure then fell the piston 12 of the senvomotor comprisingv cylinder 13 would tend to moveto the left, thus swinging the floating lever 68v about the pivot point 11 and causing the port 64 to be uncovered by movement of the valve 63 in a direction which .will release liquid from the cylinder 51 and cause the pivot pointy 6| to move to the left by action of the spring62 thus reducing the fuel injected by moving the rod 48 vwhich operates the fuel pump rack to the left, An increase in supercharge air pressure or boost produces a converse effect and causes an increase in th fuel quantity injected. 1

The centrifugal governor is shown in greater detail in Figures 5 and 6. The governor spindle 86 is driven by the engine and rotates weights 84 in the usual manner. In order that the weights 84 andthe governor springs shall not be called upon to supply suiiiciert force to operate the control linkage and fuel pump rack, this governor is so arranged that the movements of the weights control only the value of a servomotor actuated by liquid pressure. The outward movement of the weights 84 are resisted by the gover,V nor springs through a push rod 81 which thrusts on a spring carrier 88. The other ends of four governor springs 89, 60, 9| :and 92 rest against a movable piston-like abutment 93. Between va chamber 94 containing the springs and a cham- `ber 95. containing the rotating weights there -is 'aV cylinder 96 with a; piston 91 slidable Within it. The piston 91 is mounted on a-sleeve 98 in which areports 98a' and .this sleeve slides within a cylindrical'projection 99 in the end of the cylinder 9.5.

The pistony 91 has in it a radial passage |89 leading from the bore of the sleeve 98 and communicating with a space H at one side ofthe piston 91 by a passage HI through the face of the-piston. It is to be'understood that in normal working conditions the space H9 is lled with liquid. The piston 91 is urged towards thespace H0 by three symmetrically disposed springs H2 shown in Figure 6. Surrounding the push rod 81 vand sliding in the sleeve 98 is a piston valve |90. This valve is moved by the push. rod. 81 thrcughicollars" IUI and |02 pinned to the rod. The bore of the valve |00 is larger than the diameter 'of the rod 81 and it is made free Vbetween the collars so that the valve can freely centre itself in the sleeve 98.

In the end of the chamber 95 is a gear pump having a .gear wheel |03 driven by a spindle S9 and coacting with a follower wheel |04 mounted on a spindle |05. The pump draws liquid by. a drilled-'passage |00 from a reservoiry |01 and de Vlivers the vliquid under pressure to a passageI08, a relief valve, `not shown, limiting the maximum pressure 'of the.l liquid.

The operation of the parts so far describedis as follows: Assuming that. the speed'of the enginetends to 'rise then the weights 84 will tendvto move outwards compressing the spring 89 and moving the valve |00 to the left thus uncovering the inner end of the passage |09 and allowing liquid to escape :from the space H0 thus permitting theV displacement of the piston 91 to the left under the load of'the springs H2. The re'- leased liquid escapes to the right between the sleeve 98 and the valve |80 and returns to the reservoir |01 through the passage H3. The .piston 91 will move tothe left until the passage |09 is again covered by the valve |00 and the escape of liquid from space H8 is arrested. The piston 91 thus acts 'as Aa slave to the valve |00 and its movements will be in the same direction and to the same extent as the movements 'of the The movements of the piston 91 are communicated to the transverse shaft 83 bya forkedv lever arm H4 which is on that shaftand whose end bears against the face of the piston sleeve 98 under the force of a spring (not shown). The shaft 83 carries the lever' 82 (Figure 3) through 'which movement is transmitted to. the

-ra'ck of the fuel pump.V f 'It will be observed that the four governor Isprings 89, 90, 9| and 92 are of different lengths.

The springs engage between the abutment 93 and the spring carrier 88 in sequence in order to give the .governor lcharacteristic requiredi-The Adi21.'grarr1ligure 7 shows the approximatespeed of theV engine at which` each of. these springs comes into action. At idlingv speeds the spring 89 alone is in action. To increase'the spring lload on the governor 'and consequently to raise the governed running speed of the enginethe abutment 93 is moved to -theright The -rnovement of theabutment 93 is effected hydraulically, admission of liquid to the space -I I moves the abutment 93 to the rig-ht and release of liquid from the Aspace H5 allows the governorv springs to force the abutment 93 to the.left..

The c :ontroloi` the ow of liquid into .and out ofthe space H5 is effected by making the abutment piston member 93 act as a slave to a 8 valve H6. 'The abutment piston member 93 carries a ported'sleeve H1 held bye-shoulder H8 in such a manner that thev sleeve II1 can. freely centre itself in a cylindrical guide H9 fixed in theend of the chamber 94. lA land I20-of .the valve H6 controls a port |2| in the sleeve H1. if the valve H6 is moved to the. rightfthela-nd |20 of the valve uncovers Atheport "|2| vand allows liquid to `flow from the passagev |08 viaV the annular passages |22 into thevspace I I5 thus moving the piston 93 to the right. This movement of'.

the piston also moves the sleeve H1 again to bring the .port |2| fully over theland |20 -to cut oi the `flow of liquid into the space H5. The

piston 93 is now held in its new position untilv the valve I I6 is moved to a new position either to the right to raise the speed setting or to the yleft to reduce it. The control of the valve Hlmay be facilitatedby employing a rack |23 engaging va pinion |24 rotated by a lever |25. When the valve H6 is moved to the left the land I20vun covers the port |2| and liquid can escape .fromv the space I I5 through a bore |25 in valve I6, an annular clearance between the outside of rsleeve H1 and a vhousing |21 within which it` moves, and a passage H3 to the reservoir |01. In the case of the auxiliary engines 3 and 8 which drive the compressors the controls ;(see Figure 4) are similar to those shown in Figure 3 but with a modication in the methodof controlling the valve H8. In the lmain engine controls shown in Figure 3 Athis valve isunder the manual control of the driver. In the controls for the auxiliary compressor engines the Valve I I6 is con.- trolled by the pressure of the air in the air-pipe4 (or 3) that is the boost pressure. A pipe |45 v(see Figure i) conveys the air pressure in the pipe 4 (or 9) to a space |46 in a cylinder |41 '(seefFigure 4). In this cylinder a piston |48 reciprocates, being loaded by a strong spring |49 on one side and by a light spring |49a and the boost pressure on the other. The movements of the piston |48 arev communicated to the valve IIE by a rod |50. r,It will be seen that should the air pressure. in the air system rise above the required pressure, thus indicating a supply of air in excess of requirements, the piston |48 will move to the -left compressing the spring |139 and moving the valve I I9 in a direction to reduce the load of the governor springs and consequently reduce thespeed of the compressors thusreducing the air supply. The control mechanism for the auxiliary engine 3 is also shown simplified in Figure 1. Equivalent mechanism for the auxiliary engine 8 has been omitted so that the drawing shall not be unduly `complex. v 1

A power plant `in accordance with the present .invention as described above and as illustrated by the accompanying drawings asgapplied tothe propulsion of a railway locomotive may be handied in the following way.

The governor valves H6 of the four main engines are set in the idling speed position by placing a master control lever |23 in the idling position. The lever |28 is connected to the valves HG by suitable connections such `as bell crank levers |29 and push-pull rods |39. The governors are indicated in Figure l by the symbol G on the four main engines and by H on the two auxiliary engines. To put the power plantinto operation the procedure is to start the auxiliary engines 3 and 8 and allow them to run at idling speed 'in which condition .air supplied by the coinpressors 2 and l' in excess of that required by fthe supercharged auxiliary engines themselves 9 will blow oif at the loaded reliefvalves 6 and Il. The main engines are all started up and allowed to run at their idling speed.

To start the locomotive, the coupling liquid is allowed -to flow into one of the fluid couplings,y for example into couplings i3 of engine A by'v As the coul` p'ling i3 fills the load on engine A increases;y

The governor:

manipulating the scoop control 2i.

which tends to slow this engine. automatically gives this engine more and more fuel until this engine is developing full torque at idling speed and the locomotive is moving ati low speed. As the speed of the locomotive ap# proaches say 7 miles per hour the scoop control of one of the remaining engines, say for example control 22 of engine B, is operated thus allow? ing the coupling I4 to fill which gradually puts this enginev on full torque, and this procedure is repeated until all four engines are engaged. As soon as all four engines are on load, the speed of the locomotive canl be controlled solely by the single control lever 128 by which the driver alters simultaneously the spring load on all the goverV nors. At any given,vv setting of the control lever |28, the governors maintain a constant main enf gine speed irrespective of normal changes of grade or wind.

It will be appreciated that so long as only one.-

coupling for example |3is allowed to lill, its associated engine A is operating the final drivel shaft 42 with a velocity ratio represented by two differential gears in series. Assuming therefore that the differentials are such as to give a two to one ratio each, the velocity ratio when runningvvon onev engine is four to one. As the coupling I4 of the second engine fills thevtorque developed by engine B will increase until it overcomes'` 1,0 prisingvv two 4sun-,wheels and a planet-carrying member, a plurality of variable filling fluid couplings connected to drive said sun-wheels, respectively, means connecting said main engines and variable lling fluid couplings, and control means for said variable fluid couplings whereby each o f fthe said main engines may beselectively coupled jand uncoupled to a sunwheel of the said differential gear, means for transmitting power from .the planet-carrying member of the said gear to vthe mechanism whichis to be driven by the power unit, and a unidirectional brake device operative on each sunwheel of the'said'diierential gear tov prevent reverse rotation of said sun wheel .when its associated main engine is uncoupled,

and means for selectively controlling the filling ofeach of said uid couplings whereby said main "engines can becoupled either singly or together Y` to the mechanism tobe driven.

v2.` A power unit embodying the features asset out in claim 1, in which each variable filling fluid coupling is of the scoop-controlled type. 3. A power unit embodyingthe features 'as vSet out in claim l, inwhich each compressor is driven lloyan internal combustion engine operating with compression ignition and this engine has a'gov-V ernor `with means for varying the speed setting thereof,` the governor controlling the delivery of fuel to the said engine. (l. A power unit embodying the features as set out in claim 1 and inclu'diriganv internal com,-r

bustion engine operating with vcompression igni-,V tion and driving each compressor, a governor of` the centrifugal type. controlling the delivery of fuelto this engine, a plurality of springs operai. tive on the governor, means for varying the speed' i settingof the governor by movement of an vabu't 'ment forthe said springs, and means responsive tothe `boost pressure of a main engine forvarying the speed setting of the governor'by imparting-movement tothe said spring abutment. 5, A power unit embodying the features as set out in .claim- 1 and including an internal combusv tion engine operating with compression ignition shaft 42. When three engines are engaged the 'y velocity ratio for all the engines with respect to the shaft 42 is one and a third to one and'when all four engines are engaged the ratio is one to one. In this latter condition the differential gear ing is only called upon to equalise any Ldiscrepfl ancy there may be between the torques developedby the several engines. It will be seen from the above description that no discontinuity can occur in the tractive effort as the engines are successively put on to load or taken on load and owing to the presence of the iluid couplings these operations can produce no shocks to the transmission system.

It is to be noted that if necessary the improved` power plant may be arranged so that it will be possible to addthe torques of two or more engines Aso that these `will be operative simultaneously.,

What `I claim as my invention anddesire to secure by Letters Patent is and driving each compressor, a governor of the centrifugal type controlling the delivery of fuel to this engine, a; plurality of springs operative on the `said governor, a servomotor actuated by liquidunder pressure and operative to vary the `speed setting of the governor by movement ofari irv abutment for the said springs, means for confv trolling' the said servomotor in accordance with.

. theboostpressure ofthe engine, and ra servoif motor actuated by liquid under pressure. and

operative to transmit from each governorthe movement which effects the speed regulation. of

the engine .with which the governor is associated. v GIA power unit embodying the features as set outin claim 1 wherein the sun-wheels of said d iierential gear carry brake drums and'in which eafch of the said unidirectional brake devices is 1. A power unit comprising in combination two i main internal combustion engines each operating with v'compression ignition, means includingiat v tures set out in claim 1 andgwherein` the `said least onecompressor driven independently of said main engines and serving to supercharge them, a plurality of engine speed responsive governors each of which controls the fuel injection pump of a main enginevineans for varying the speed setting of each governor, a differential gear comof the self-wrapping type operative on a 'brake drum carried by a a sun-wheel to'gr'ip said drum automatically and hold it stationary when the sun wheeland drum tend to rotate in one direc* tion and to release said brake drum automatically when it is rotated in the .,:opposite direction;

71A'powerl plant comprising-lin" combination. two'power units each of which embodies the feaplanet-.carrying member ofthe differential gear of each power unit is rotationally connected to theirsunQwheel o-a'lseparate differential gear 'i se planet-carrying member is rotationally absence automatic'` control system associated' withl each main engine' and comprising a governor'responsivel to variations in the speed of the engine'and operative to control that speed, pneumatic means responsive tothe boost pressure of the engine,

and/'means' a'ctuatedby said governor conjointly with said pneumaticv means for varying the amount of fuel delivered to the main engine.

10. A power unit embodying the features'as set out in claim 1 in which the main engines have air manifolds and including in combination an automatic control system associated withV each main'engine and comprising a governor respons ivesto variations in the speed of the engine and operative to control'that speed, a servomotor including a'cylinder with aipiston therein, a p ort in the wall of the cylinder at one side of the piston 'with 'a communication between this port and the'air manifolds of` the engine, springs of diieren't strengths respectively acting on each sideI` ofv the said servomotor piston with the stronger spring at the side of the piston remote from" the. said port in the Wall ofthe cylinder, means for varying the lfuel supply to the engine inaccordance with-'the movements responsive tov boost pressure ofthe said servomotor piston, and' means 'for Aalso varying the amount of fuel deliveredto'the engine iby operation of the governor.

11. A power unit embodying the features as set outA in claiml in which the-mechanism associated withgjeachgovernor controlling an engine comprises in combination a casing enclosing the governor and 'its weights, a shaft through which the governor is rotated, a" -push rod coaxial with the said driving shaft and to which movement in the direction ofthe governor axis is imparted by the governor Weights, a servoniotor enclosed in the said casing and including a cylinder and' piston Y 12 said-'valve'in accordance Vwith the speedof the engine, and means foralsoactuating-the said valve in accordance with 'theboost 'pressure'of' theengine.

13. A power unit embodying the features asset out in claim 1 in' which the control of cachengine is effected by hydraulic `means utilising oill under pressure obtained from the lubricating system of the engine and including fluidfpressure responsive means connected to the fuel Ainjection pump 4control whereby if the pressure in the saidsystemv falls below a predetermined figure ther vautomatic control of the fuel supply can-be overridden Vand the delivery of fuel by the fuel pump.

stopped.` l

14. A powerunit embodying'the featuresfas set out in claim 1, including a safety control means for stopping the Ydelivery of fuel by the fuel pump rof veach main engine, hydraulic means utilizing 'oil under* pressure obtained from the'lubricating system of said main engine for maintaining said safety control means in an inoperative position Jwhen said pressureexceeds va predetermined value,

and'means for moving' saidsafety control means into an operative position when said pressure falls'below said predetermined value.

15. A power unit comprising in combination two rinternal combustion engines each operating with compression ignition, a fuel injection pump for each engine, a compressor driven independently of said engines and connected thereto to supercharge them, a plurality of engine speed responsive governors each of which controls the fuel injection pump of one of said engines, selective means for varying the speed setting of said governors, a differential gear comprising vtwo sun wheels and a planet-carrying member, a variable filling fluid coupling connected to drive each sunwheel and individual control means for -said fluid couplings connecting said engines respectively to said couplings whereby each of said engines may be selectively coupled and uncoupled to its corresponding sunwheel, meansy for transmitting power from said planet-carrying member to the mechanism to be driven by said'power unit, and a unidirectional brake device operative on eachsunwheel to prevent reverse rotation thereof when therein concentric with 'the said push-rod, a valve controllingV the flow of vliquid under pressure to and from the cylinder` of` said servomotor the valve being. concentric with the servomotorand actuated through the'. saidpush-rod .by the governor weights, means by which movements of the piston of .thesaid servomotor are caused to adjust the rack ofthe fuell pump of the engine and vary the-'fuel sup-plyl to the engine, at least one spring acting on the governor weights, and hydraulic means for moving an abutment of said spring andV thereby varying the setting and operation ofthe governor.

12. A power unit embodying the features as set out inclaim 1 invwhich the control of the fuel supply to each engine-is effected automatically byl apparatus which includes a fuel supply pump having a rack and a-.servomotor actuated by liquid under pressure and operative to set the rack of the fuelsupply pump, a piston valve controlling the servomotor, means for actuating the uncoupled from an engine, whereby said power unit operates to transmit the torque of either or both .engines to said driven mechanism progres-l sively and uniformly during coupling and uncou-l pling thereof at allVv running speeds.

LOUIS FREDERICK"RUDST-ON' FELL'.

REFERENCES CITED The following referencesare of record in 'the vfile of this patent:

UNITED STATES PATENTS 

